[TomT/Williamsburg]

In my experience this is true - over time it finds or makes leaks. Had a 2000 Honda that I ran synthetics oil in. After about 8 months I developed a leak that mechanics said was the rear made n seal - the b expensive proposition. I had read about the sing synthetic oils in older cars and the subsequently leaked. Switched back to conventional oil and the leak went away.

May not work in all instances/situations but it seems to be prone to leak older cars.